Machine-switching telephone system



L. POLINKOWSKY. MACHINE SWITCHING TELEPHONE-SYSTEM.

APPUICATION man DEC-6, 1918. 1,412,572. Patented p 11, 1922.

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L. POLINKOWSKY. MACHINE SWITCHING TELEPHONE SYSTEM.

APPLICATION man 050. 6, me. I 1,412,572. w Patented Apr. 11, 1922. I y ISHEETS-SHEET 2. 2 7 i2. I52

/nve/7/0/ L/pa Po/M/wwsky Patented Apr. 11, 1922.

Z $HtETS-SHEET 4- L. POLINKUWSKY.

MACHINE SWITCHING TELEPHONE SYSTEM.

APPLICATION FILED use. 6. 19m.

/n vemor: L ipa/ alinkawsky. h ,5 A iiy L. POLINKOVWSKY.

MACHINE SWITCHING TELEPHONESYSTEM.

APPLICATION FILED DEC-6.1918.

1,412,572. Patented Apr. 11, 1922.

7 SHEETSSHEET 5.

my. 5, .l

lnveriiol A $4 Po/m/vo Wsky.

' L. POLINKOWSKY. MACHINE SWITCHING TELEPHONE SYSTEM.

. APPLICATION FILED DEC- 6| 9H1- 1,4 1 2,572, Patented Apr. 11, 1922.

l$HEETS-SHEET 6- FIG. 6.

Aff 'y.

L. POLINKOWSKY.

MACHINE SWITCHING TELEPHONE SYSTEM.

APPLICATION FILED D50. 6, 191-8- Patented Apr. 11, 1922.

ISHEEIS-SHEET 7.

[1 04 Po/Uv/ro wsky- UNITED STATES PATENT oF IcE'.

LIPA POLINKOWSKY, on LONDON, ENGLAND, ASSIGNOR TO WESTERN ELECTRIC COM- PANY. INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YO MACHINE-SWITQHING TELEPHONE SYSTEM.

Specification of Letters Patent. Patented Apr. 11, 1922.

Application'filed December 6, 1918. Serial No. 265,600.

"0 (IN 'w/iom' it may concern:

iile it known that 1, L123 PoLnqnowsKY, a citizen of Russia, residing at T il'csthourne Terrace, Hyde Park, London, W., England, have in-iented certain new and useful linprovenien in 7 Machine-Switching Telephone Systems of which the tollowing is it full. clear, co .cise, and exact UPClllsflJlOfl.

This invention relates to mach ne .nching telephone systems end more iticularlx to machine switching; telephone systems or the semi-automatic type in which calls are extended over ooerators positions on which the calls receive full supervision.

I: feature of the'j'. mention is the provis on oi circuits and apgaraius for enabling the calls initiated during the slack or nonbusy hours; at a small exchangelocated in the same area us a large exchange. to he automatically extended to an opeintors position such large exchange.

Another leature oi the invention s th ,rovision of ineans for converting some or he trunlriines extenijlingr hetween the large sma l e, 'l i'oin the culin ry day 1:. in l exchanp 2 "vice trunks.

Still another feature oi? the in small exchange for day service, in suitable for extending cals an op nosition at the large excl ii still. "further feature 7 ans, one relate-til to the last named i. :ture. is the :3: rrision of circuits and apparatus so honverti the switches ol the small exchange. wh .1 give full -=.u; ei:ision including release under centre at thesinull c- 3 l hengc. that Sud supervision,

riitinted at the change and extended to an opera the 1 re exchange, is nut such l on 'lurljhqr feature oi the ii provision o'l' circi nd apparatus for anti i'zifatic-nlly testing at the initiation oi the exchange.

conversion, the condition existing 011 the ture. is an arrangement of circui s and appsiratus to an.zomaticully test the ends of the of the operator mention the" exchange, and to delay also the conversion,

in the large exchange, of a trunk until such trunk becomes free.

A particular featureof the invention is the provision of means for automaticallyinitiati'ng the conversion of the trunks and switches from day to night service when all the operators positions at the small exchange are vacant, and to automatically restore the trunks and switches from night service to day service when an operators position at the small exchange is placed in service.

Fig. 1 shows a suhscribers line and a first line finder.

F 2 shows a cord consisting of a second line finder and a first group selector. i

Fig. 3 shows the searching sequence switch of the cord and an operators position indicated. so far as is essential for the understanding of the system.

Wig. 4 shows a common arrangement which controls the necessar 1 change over from day automatically when all oi ierators positions in the exchange are vacant and autoinnth cally removed as soon as one o? the positions isoocupied by an operator.

Fig. 8 shows :1 cord used for only.

Figure 9 shows a diagram of two e. changes and. interconnecting trunks.

The system disclosed as embodied in the 'u'esent invention will be best understood from a description of the operation thereof and reference to 'United States Patent No. '1 160181, of i ovemher 16, 1 915. to F. R. Mc-

day service Berti and D. Koenig", and United S .nes

Patent No. 1,193,053. of August 1, 1916; to L. Polinkowsky; fully describing the analogo'us circuits disclosed in the present inrention.

In order to enable, during the night, the use of second line finders and trunk lines which are also used during the day. the cirgized and moves from position l into positained closed over contacts or the special sequence switch 100. p v

The contacts of this sequence switch are differentiated. from the contacts of sequence switches 220 and 25-0 by showing them solid. Further the contacts and relays associated with the sequence switch are designated by numbers in the one hundred group of numerals. r

During the day sequence switch 100 is in position 1 and its contacts remain without influence on the operation of the cord which is, briefly stated, such that a line relay 201. is operated and causes the operation of the common starting relays 204; the power magnets 211 of the free first line finders in the group are energized and the line finders search for terminal 210 of the line, in reaching which test relays 214i and 212 of the line finder are energized; the power agnet 211 is disconnected and the holding magnet 215, together with the common starting relays 216, is energized. At the free cords, the line finders of which have access to these first line finders, the relays 252 are energized and cause the energization of the power magnets 261 so that the brush carriages ot' the second line finders rotate and the test relays 2G4 and 262 of the line finder which first reaches the terminal 230 are energized, disconnecting the power magnet 261 and energizing theholding magnet 265. Sequence switch 250 of the cord is also energized, starts from position 1 and moves into position 4-. In passing position sequence switch 220 of the cord is also energized, starts from position 1 and moves into position at. Relay 227 is thereby energized together with relay 213 of the first line finder and the cut-ofi relay 207 of the subscribers line. The letthand windings of therepeating coil 229 and the supervisory relay 231 are brought into circuit with the calling line, and the calling lamp 270. together with pilot lamp 372 are lighted. Sequence switch 380 is now energized and searches for a connection with a free register of the operators position and, assuming the A register free, is arrested in its position .1 or 7 inwhich the test relays 264: and 262 are again energized and sequence switch 250 moves from position 4 over position 5 into position 8. When sequence switch 250 passes position 6 sequence switch 220 is again enertion The calling lamp 2'70 is thereby con nected with an interrupter 236 and .disjlays a flashing signal before the operator. The operators telephone is now connected in bridge to the "calling line. When the operator depresses the number keys, not shown. according to the number required, sequence switch 220 moves out from position 5 into position 8, in which the ringing lamp 240 displays a flashing signal. The fundamental circuit containing the stepping relay 32a of a register is first closed over relay 252 which is energized and causes the advance of sequence switch 250 into position 9 in which the trip spindle 273 rotates. At its contact 275 short-circuitings are provided to the fun damental circuit andafter the first series of impulses is completed relay 252 is de-energized and sequenceswitch 250 advances from position 9 into position 10 in which the test relays 264i and 262 are brought in connection with brush 276 of the first roup. selector, whereas the power magnet 281 of the selector brush carriage is energized and the brushes are moved along the terminals in the row de termined by the position or" the trip spindle. Itelay 252 is thereby maintained energized over the register circuit. After finding a free second selector the test relays 264 and 262 are energized, the power magnet 253i is disconnected, while the holding magnet and sequence switch 250 are energized. Sequence switch 250 is advanced fromv position 10 over position 11 into position 12 in which the fundamental circuit is extended to the second group selector. After the completion of the selection the register is released and relay 252 is de-energized;-sequence switch 250 moves into position let. i i hen the sequence switch of the final selector usel for this connection is passing over its busy position, supervisory relay 242 is energized and sequence switch 220 moves from posi on 8 into position 9 and when the sequence switch of the final selector leaves the busy position, relay 242 is tie-energized and sequence switch 220 moves from position 9 into position 11 in which the ringing lamp 240 lights. When the called subscriber answers and a through connection is established at the final selector, the right-hand windings of the repeating coil 229 and relay 2&2 are brought in con nection with the called line, relay 242 is again energized and the sequence switch 220 moves into position 14. After the conversation is completed andthe clearing out signals 235 and 245 are displayed before the operator she depresses the release key 280 of the cord and causes the energization-ott release relay 263 which in turn causes sequence switch. 250 to move from position 14 into position 11.

When sequence switch 250 reaches position 15 the sequence switch 220 is started and moves from position ltinto position 1; la passing positions 1.6 to 18 the metering hat tery 359 is connected to the calling line and the meter 208 is operated. lVhen sequence switch 220 reaches position 18 relay 25:. is energized and causes-the advance of sequence nection on which relay key 365.

switch 250 from position 17 into position 18 in which t 1e brush carriage is restored to its position of rest. wherehy after the home con tact 289 (it the brush carriage is closed rela 262 is energized. together with the holding magnet 285 and sequence switch 250 moves into position 1. i

If the called line is busy relay 242 remains continuously energized and sequence switch 220 remains in position 9 in which the lamp 235 is connected to an interrupter 246 over contact 248. bottom, in position 9 and displays a busy signal before the operator. The secondary winding of the common busy tone coil 24'? is connected in bridge to the line and the operator in depressing the listening key 239 can communicate with the sub- ECzllJCI. She releases the connection. after the subscriber has restored his receiver, by depressing release key 280 to'energize relay 263 and causes sequence switch 250 to inoye into position 17 and open the circuit torrelay 227 before-sequence switch 220 leaves position 15 causing the energization. of relay 224. which hinders the metering. The meteris also hindered it the release is made when sequence switch 22!) is in the ringing position 11 and the called subscriber does not answer. To force the release of a conll is energized-or i. the calling linc.the operator deprc .s the release key. 280 or" the cord and the forced release ke at her osition; To bring the switches ot the connection in a holdorer ondition, whereby the calling); line is made tree. the operator depresses the listening: key on the cord and the common holdover Relay 225 thereby energized, the sequence switches individual to the switches used for a connection are advanced into position in which the switches are held up. whereas the calling line' is made tree. lVhen the operator desires to hinder the metering" of a successfully established con,- nection, due to the complaint of the subscriber. she depresses the'common. meteringhinderine key 364: before depressing the individual release, key 280 and the metering; hatteiv 359 is disconnected during the release.

For night service key 420, 4-, isv denressed and th commonsequence switch 400 is energized. in a circuit over contactf406 ton nd contact of key :20. Sequence switch a. 1-00 starts from position 1 and moves under the control of its local contact e01 into position 10. l hen sequence switch 400 reaches position 2 each sequence switch 100 individual to a cord used during the night serv ice is energized in a circuit over its contacts 105 top and a contact of sequence switch L00 corresponding to contact 402 top. Sequence 100 starts from position i and moves .unucr the control 0t its local contact 101.

into position 2. In position 2 of sequence nection. One sequence ewitcl'i M is use;

only. Such a cord is shown in switch 400 relay 479 at the main exchange is also energized over a separate trunk 43a) and contact 403 oi sequence switch +100. Relay 4'79 causes the energization of sequence switch 160 over contact 462 hottom and front contact of relay 4T9. Sequence switch 4-60 starts from position 1 and moves under the control of its local contact 461 into position 2. In position 2 of sequence switches 100 and 460 a test is made to determine waether or not trunk lines which are to be used for night service are involved in a conin the distant main exchange for several trunk lines. Each trunlr line is rovided with a relay 4-63 wnich is connec id over contact 4.64 of sequence switch 460 in position 1 to the test terminal 465 i it the trunk line is busy relay 4L6?) energized and maintains its connection over its richt-hand front contact. If all the trunk lines controlled hy sequence switch are tree a circuit is established for the energizotion of sequence switch 460 over contact- 466 and the left-hand back contacts of relay 4-63 and the corresponding' relays 46 and of the "'iUfi remaining trunk lines. Sequence switch 460 then starts from position 2 and moves into position 10 in which overcontacts 469 and 470, the trunk line is connected to the terminals ot a group of second line finders and to a line relay 47K; The second line finder in the main exchange belongs to a cord arranged in the same as the cords in the smallerexchange used for day service A T he cord is connected to an operators position in the same way as indicated in Fig. 4. A comparison of l. with Fig. 8 will make clear the difference in the circuit of the cords specially arranged in the smaller exchange for night service. In position 2 of sequence switch 460 Fig. 5 a circuit is closed tor the encrgization oi sequence switwh 490 over contact 481. top. of sequence switch L60 and contact l-92.'hottoni, of sequence switch 490. Sequence switch 490. Which controls t'urther trunk lines. star om position i and moves into position 2 in which over its contact e96 top a similar test is made to determine whether or not the correspond trunk lines are free. after which sequence switch 490 moves into position TO. Sequence switch 100 when in posit connects. over its contacts and 103. the line finder oi the cord to the other end ot' the trunk line. whereby For night service a ltlll seque switch 350 of the operators ,iitil the ouence switch +61) u? rsemi trunk li ies has also been advanced to position 1 1). quence switch 1.00 therefore in position 2 undertakes a test as to whether not oniy the trunk line 450 but also the other trunk lines controlled by the sequence switch 4.60 are "t'ree which is the case it their sequence rrom pot tion 10 urovidi l I a number chan es in the circuit c coral: Fieveral contzicts on sequence switm 1:60 are also utilized to aid in the changes required: at contact 404lo't sequence switch 106 the common conductor 306, which connects the calling; lamps 270 of the cords to the pilot relay 358 of the operators posit-ion is opened and at contacts similarto contact 4i05 the connections from the common starting relays 216 01" the first line findo" o cups to therelays 252 of the correspond cords are closed, re-establishing over i r 431 and 4-32 the circuits whiclilare lqe ot opened at contac s similar to contact 352 oi the timing sequence "posit-ion in position 12, The number oi contacts similar to contact 105 of sequence switch 100 is equal to the number t cord groups, each he access to sixty line nnileis whereas the number 0t contacts similar to cont-act 402 is equal to the number of cords used for the night service, whereby only iiew cords in each group are sufiieient dm'ag the night "for each sixty first line finders.

At contact 106 top 011 sequence switch 101) in position 10 the left-hand high resistance winding oi relay 264 is disconnected from contacts 353 0)? the tim ng sequence switch 350 and connected to contact 255 bottom oi sequence switch 250 re-estahlFishing the connection opened at contact 353 ct sequence switch 350 in position 12.

When the brush carriage of a first line finder is arrested on the terminals 01 a oalling line and the startin relays 216 are energized, relays 252 oi each tree cord which has access to this firstline finder are energized in a circuit over the contact 253 of sequenc switches 250, conductor 1W, contai'zt 465 of: ice switch 200, conductor 451 and front contacts of common starting re ys 216. The power magnet 261 01"- the second line finder is thereby energized in a circ it over contact 25 1 top of sequence switch back contact of test relay 262 and front contact of relay 252. The brush carriage or". the second line finder rotates. When the terminal 230 of the calling first line finder ing of relay 264-, contact reached: relay 26% is energized in a circuit including contact 255 bottom of sequence switch 250, contact 106 top of sequence switch 100, left-hand high resistance wind- 6 0' sequence eo's switeh 250, terminal 230 r i tance 21? front contact of relay 212 and back contact of relay 213. Relay 26 llHlIIQS. over its front Contact, its right-hand lo resistance winding tog-ether with winding; of relay 262 in parallel to its high resistance winding. Terminal 230 is made busy an relay 262 is energized The power 261 is disconnected on back contact of this relay whereas over its trout cont-act is caused the energization 01" sequence switch 250' in a circuit includingcontact hot tom of sequence switch 250 and frontcon tacts of relays 262 and In parallel to the sequence switch is also connected over its contact 260 the holding magnet ot' the line finder, the brush carriage is rested, whereas sequence switch 250 starts from position 1 and moves under the con trol of its local contact 251 into position i. Theenergization oi": relay 349 parallel to magnet 265 remains without effect on the timing sequence switch 350, which is not 3 its position 1 When sequence switch 250 passes over position a circuit is es"sblished for the energization of seque switch 220 over contact 222 bottom, contact 266 bottom of sequence switch 250, lefthand back contact of release relay 2625 and contact 258 top of sequence switch 250. Eh que'nce switch 220 starts from position 1 and'moves into position at. In position 2 of sequence switch 220 a circuit is estab lished for the energization oi cut-off relay 207 of the subscribers line, relay 218 of the first line finder and relay 227 of the second line finder including terminals'218 and 22o,

left-hand back contact of holdover relay ,magnets of the tree first line finders are thereby-deenergized and the free first line finders are arrested. Also the holding; mag;- net 215 of the hue finder in question and the common starting relays 216 are de-energized and the relays 252 of the free cords are tie-energized, causing the de-energization of the corresponding line finder magnets 261, so that the free second line finders in the group are arrested. Also the test relays 26t and 262 or the cord in question are Clo-energized. Relay 227 provides over its front contacts the connection of the calling lll) line with the left hand windings of the repeating coil 229 and the supervisory relay 231, the circuit including sequence switch contacts 232 top and 233 top of sequence switch 220. Relay 231 is energized and provides the short-circuiting of the right-hand high resistance winding of release control. relay 121 in a circuit over front contact of relay 231 and contact 107 bottom of sequence switch 100. The energization ot quence switch 330 of the cord in position 4 of sequence switch 250 is hindered through opening of. the circuit at contact 106 bottom of sequence switch 100, sequence switch250 remaining in position 4.

The connection of the test relay 26 i to conductor 309 and contact 333 of sequence switch 330. which is in the day time maintained over sequence switch contact 268 of sequence switch 250. is now removed on contacts 109 and 110 of sequence switch 100 and the sequence switch contact 268 is utilized to establish a metallic connection to the trunk line. The metallic circuit is closed over winding of line relay 4:71, left-hand back contact of cut-off relay 4:72, contact 470 of sequence switch 460. one wire of trunk line 450, contact 103 bottom of sequence switch 100, upper right-hand winding of repeating coil 229. contacts 111 top and 109 top of sequence switch 100. contact 268 bottom of sequence switch 250. contact 110 top of sequence switch 100. left-hand low resistance winding of relay 121. contact 107 bottom of sequence switch 100, front contact ofrelay 231, contact 112 bottom of sequence switch 100. relay 2 12, contact 102 bottom of sequence switch 100. second wire of trunk. line 450, contact 469 of sequence switch 460 and back contact of relay 477. Relay 4171 in the main exchange and relay 121 in the small exchange are thereby energized. Both windings of the common starting relays 474 are energized in a circuit over the front contact of relay 4.71. whereas a potential is created at terminal 41-80 over the individual resistance 473 and back contact of relay 172. The free second line finders of a group of cords in the main c3:- change aresearching for terminal 480 and as soon as the brushes of a line finder of a cord, shown in Fig. 8. reach this terminal relay 664 corresponding to relay 264 is energized and terminal 4-80 is made busy. Relay. 662 corresponding to relay 262 is also energized. the brush carriage isarrested, whereas sequence switch 650, corresponding to sequence switch2-50. is energized. started from position 1 andmoved into position 1. In position 2?); of sequence switch 650 sequence switch 620is also energized. started from position 1 and moved into position 4. When sequence switch 620 is in position 2 a circuit is closed for the energization of relay 627 on the cord and relay 177 on the trunk line including terminal 178 and contact 623 of sequen e switch 620. Re-

lay 121 is thereby maintained energized in a metallic circuit over both front contacts of relay 627, contacts 632 and 633 of sequence switch ,620, supervisory relay 631 and right-hand windings of repeating coil 629, whereby the relay 627 is energized he tore the slow-operating relay 477 is able to disconnect the circuit over its back contact so that the relay 121 does not become dcenergized during the change over in the circuit. The cord obtains a connection with. a tree register set and the establishment and supervision of the connection in the main exchange remains the same as for a local -all.

WV hen the calling subscriber restores his receiver on the hook, relay 231 is de-ener gized and the shunt around the high resistance winding of relay 121 is opened, causing the de-energization of relay 631 in the main exchange, and the lighting of clearing-out lamp 645. After the operator receives both clearing-out signals 645 and 635 she depresses the release key 680. During the release of a successfully established conversation the metering battery in the main exchange is connected over contact 623 of se quence switch 620 to terminal 78 and the marginal relays 4:75 and 4576 are energized and connect temporarily the trunk line to a source of alternating current. This causes the energization of relay 122 which, in series with a condenser, is connected in bridge to relay 121. The right-hand winding of relay 123 is thereby energized in a circuit over front contact of relay 1.22. Since contact 632 is opened in position 15 oil sequence switch 620. whereas the ineterinpcircuit is closed at sequence switch contact 623 in position 16, relay 121. is (lo-energized before the metering starts. It provides a circuit "for the energization of the left-hand winding or relay 263. including contact 113 top of sequence switch 100, contact 249 of sequence switch 220 and contact 114 bottom of sequence switch 100. The right-hand winding of relay 263 is maintained energized in a holding circuit over its right-hand front contact-and sequence switch contact 255 top. Relay 263 closes at its left-hand front contact a circuit for the energization of se quence switch 250 which leaves position 4. In position 5 sequence switch 250 is maintained energized over contact 258. bottom, contact 108 top of sequence switch 100, contact 267 bottom of sequence switch 250, back contact of relay 262 and front contact of relay 252. Sequence switch 250 therefore passes position 5 disregarding the position ofsequence switch 330 and moves over positions '8, 9, 10, 11, 12 and 14 into position 17.

7 When sequence switch 250 passes position .tact of relay 477 t 6 sequence switch 20 is energized in a circuit over contact 234 bottom, contact- 271 top of sequence switch 250 and right-hand back contact of relay 225. Sequence switch 220 starts from position 4 and moves into position 5. When sequence switch 250 reaches position 15 sequence switch 220 again energized in the circuit as described. and moves into position 9. Relay 121 is energized in position 9 of sequence switch 220 in a circuit from ground over contact 115 top of sequence switch 100, contact 24% bottom of sequence switch 220 contact 116 to) 112 bottom and 102 bottom otseruencc switch 106 one wire of trunk line 450, contact 469 of sequence switch 461), back con battery. Sequence switch 220 is energized in a circuit over contact 234 top, contact 117 bottom of so quence switch 100 and lront contact oi: relay 121. Sequence switch 220 starts from position 9. In positions '11 and 14 sequence switch 220 is again energized in the circuit over contact 271 of sequence switch 250. Sequence switch 220 advances into position i. In position 18 of sequence 22) relay 252 is energized in a circuit orer contact 269 top of sequence switch 250, contact bottom of sequence switch 220 and back contact of relay 242. Sequence switch 250 is now cner gized over :front contact of relay 252 and moves into position 18, in which since the brush carriage of the group selector is in its home position, contact 289 is closed. relay 262 is energized and sequence switch 250 is advanced into position 1.

Relay 123 having been energized disconnect-s on its left-hand back contact the right-hand winding ot' the non-1netering relay 224 from the back contact of relay 227 and connects this winding; over the letthand high resistance winding of relay I23 and contact 255 top of sequence switch 254). Relay 123 maintains thereby energization, whereas relay 224 remains (lo-energized. Over the right-hand front contact of relay 123 the circuit -for relays 227 213 and 207 is maintained closed independent 01' sequence switch 250. When sequence switch 220 passes over positions 16-1-18 the metering battery is temporarily connected at sequence switch contact 223 with terminal 230 and the meter 208 oil subscriber line is operated.

If the disconnection is made in the main exchange without metering, relays 476 and 475 remain (lo-energized so that relays 122 and 12 3 do not operate. Vlhen th release oi? the cord proceeds. as has been described, sequence switch 250 reaches position17ainl in opening its local contact 251. provides the de-ener ization oi relays 227, 213 and 207. Relay 227 when (lo-energized causes the energization of the non-metering relay 1124 in a circuit over lett-hand back contact of relay 227 and sequence switch. Contac .331

Relay 224 maintains its energization over its left-hand winding and its left-hand front contact and disconnects on its right-hand contact the connection to the metering battery. Nhen sequence switch 250 reaches posit-ion 18 the left-hand winding ot relay 224 is short-circuited on contact'272 oi. sequence switch 250 ant. relay is decnergized.

It a disturbance occurs on the switches the operator in the main exchange is able to hold all the switches used for the connection but to free the calling line by depressing the holdover key on her position together with listening key 639 of the cord. The right-hand winding of relay 625 is thereby energized and the circuit of relay 627 is opened on left-hand hare contact of" relay 625. Over the right-hand front contact of relay 625 relay 642 is energizedand the sequence switch 620 is advanced into position 14. When the quick falling ollj' relay 627 is deenergized a circuit is established over the right-hand back contact of relay 627, including the relay 6 31 terminal 480, right-hand trout contact of relay 472 and left-hand winding of slow falling oil relay 477. Relays 477 and 472 remain thereby energized, whereas the potential on terminal 480 corresponds to a busy potential so that another second line finder cannot be arrested on this terminal. r'hen the trunk line is opened at the "front contacts of relay 627 the release of the switches in the outgoing: exchange starts" as has been described, whereby sequence switch 250 is advanced into position 17 and the calling subscriber line is made tree. Sequence switch 224) is arresed in position 9 since relay 121 remains de-energized. Relay 224 is thereby energized'as described but does not influence the calling line since the right hand arn'lature of relay 224 .is disconnected from groundat contact 118 oi. sequence switch 100.. Over the right-hand. back contact of relay 227 the right-hand winding of the slow falling off relay 213 is maintained energized in'a circuit including relay 231 and terminal 230.

If relay 262 in position 2 of sequence switch 250 is de-energized, which may be the case when two second line finders happen to stay on tlie same terminal of a calling first line finder and both relays264 become energized but are not able to maintaintheir energization atter sequence switch contact 255 bottom is opei'ied andthe high resistance winding is disconnected, relay 263 is energized in a circuit oyer rest contact of release key 280, sequence switch contact 267 top, back contact of relay 262 and front contact of relay 252. Sequence switch 250 is energized in a circuit over left-hand front contact of relay 263 and sequence switch contact 258; and the sequence switch 250 completes its rotation without starting sequenoe switch 220, the circuit of which is opened at the left-hand back contact of relay 263.

When the key 420 is restored sequence switch 400 is energized in a circuit over its contact 406 bottom and rest contact of key 420. Sequence switch 400 starts from position 10 and moves into position 1. Sequence switch 100 is energized in a circuit over contact 105 bottom and contact 102 bottom of sequence switch 400. Sequence switch 100 starts from position 10 and moves into position 11. In opening of contact 403 of sequence switch 40-1) relay iii-9 is (lo-energized and sequence switch 460 is energized in a circuit over its contact 462 top and back contact f relay 4J9. Sequence switch 460 starts from position 10 and moves into position 11 in which sequence switch 490 is energized in a circuit over contact 492 top and contact 4:81 bottom of sequence switch 4:60. Soquence switch L90 moves from position 10 into position 11. Sequence switch 460 can not move from position 11 it one of the trunk lines controlled by this sequence switch is still engaged in a night connection. In this case the common relay 182 remains energized together with relay M2 'ot the trunk line. After the trunk lines in question are free on the outgoing end, sequence switch 460 is energized in a circuit over contact 466 bottom and baclt contact of relay $82. Sequence switch 460' starts from position 11 and moves into position 1. making these trunk lines free for day service. In a similar way sequence switch s90 moves from position 11 if relay 493 of the corresponding trunk line is (fie-energized.

Sequence switch 100 cannot lie-restored to position 1 unless the cord is free and its sequence switch 250 is in position 1;

when that is the case sequence switch loll is energized in a circuit over contact 10% bottom and sequence switch contact bottom sequence switch 100 starts "from position 11 and moves into position 1.

In Fig. 7 the control of the operation of a sequence switch 410- similar to sequence switch 100 in'Fig. 4 is made automatically .over contacts ill 4.12 and 413 the oper-' ators telephone jacks. whereby it the con-- i is energized in a circuit over contact 416 each sixty first line finders in addition to the co .4 used it)? day service there are prosided a few special second line finders which have access to the same term inals and which are used only during the night service. The special line finders are connected in a similar way to trunk lines which are used in the day for callsoutgoing from the main exchange to the small exchange, where they are connected to group selectors. "hen the night service key 520. correspondingto key 420. is depressed sequence switch 500, corresponding to sequence switch 400. is energized in a circuit over its contact 506 top and contact of key 520. Sequence switch 500 starts from position 1 and moves under the control oi its local contact 501 into position 10. Scquence switch 550 of the second line tinder used for night service is thereby energized in a circuit over contact bottom and contact 502 top of sequence switch 500. The sequence switch 550 starts from position i and moves into position 2. The trunk lines used for night service are at the main 0:;- change under the control oi sequence switches as shown in Fig. 4. In position 2 of sequence switch 500 Fig. 5 the circuits which control the sequence switch in the main exchange are closed at contact 503 over a special trunk line. as has been described, and since in the main emhango several trunk lines are controlled by one sequence switch it is essential that a second line finder shall not obtain a connection with a calling first line finder unless the corresponding sequence switch in the main exchange has also prepared the other end of the trunk line. So quence switch 550 can therefore become encrgized in a circuit over contact 554; bottom. contacts 5540, 54:1 and 542 of the sequence switches on the corresponding group selectors of the trunk lines it all those sequence switches are in position 1. Sequence switch 550 then starts from position 2 and moves into position 3. The connection to the group selector is then opened at contacts'552 top and 553 top of sequence switch 550. The power magnet 561 of the line finder can now become energized in a circuit over contact 556 bottom of sequence switch 550. back contact of test relay 562 and front contact of common starting relays 216 shown in Fig. 1. When the terminals of the calling first line finder are reached relay 56 1 is energized in a circuit over sequence switch contact 557 top, rigl1thand winding of relay 5'?" sequence switch contact 558 bottom. to. ash 5G0. resistance 21.7, in Fig. 1, front contact of relay 212 and back contact of relay 213. llc

lay 564i brings. over its front conta t. its left-hand winding and the winding oi rclirv 562. in parallel to its righthand winding. The calling terminal is made busy whereas relay 562 is energized. disconnects on its back contact the power magnet 561 and providcs over its front contact and over sequence switch contact 55 i top the encrgization of sequence switch 550. in parallel to the sequence switch the holding magnet 565 is connected over contact 559 bottom, the brush. carriage is arrested, whereas sequence switch 550 is started from position 3 and moved into position 7. -\Vhen sequence switch 550 reaches position 5 a circuit is established for the energization of relay 567, relay 213 on the first line Finder and the cutoff relay 267 on the subscriber line, including brush 566, left-hand back contact of relay 563 and sequence switch contact 566 top. Relay 567 connectsv over its front contacts the left-hand windings oi. the rcpcatingcoil 569 and the supervisory relay 571 with the calling line. Relay 571 when energized provides a shunt around the left-hand high resistance winding of the release relay 572. In position 7 of sequence switch 550 the right-hand windings of repeating: coil 56%) and the relay 572 are'connectcd over se quence switch contacts bottom and 553 bottom to the trunk line. Belay 572 as well as relayt'r'l in Fig. 3 are energized and the call is extended to the main exchange where a connection is established over a cord such as shown in Fig. 6.

When the connection is released in the main exchange and sequence switch 620 leaves position 14, opening its contact 632, relay 572 is (lo-energized and sequence switch 550 is energized in a circuit orer contact 555 top and back contact of relay 572, sequence switch 550 starts from position 7 and moves 574:. In position 14: of sequence switch 550 relay 572 is energized in a circuit from ground .over sequence switch contact 575 top, relay 572 both windings, sequence switch'contact 552 bottom, one wire of the trunk line and back contact of relay 47 7 to battery. Sequence switch 550 is then energized in a circuit over contact 554Jtop and front contact of relay 572. Sequence switch 550 starts-from position l moves into position 1. In passing positions 15 to .17 the metering battery 576 is connected at sequenceswit'ch contact 566 to the brush 56S, and the meter 208 of the subscribers -line is operated. When a connection is released in the main exchange without metering, relay 563 is energized in position 13 of sequence switch 550 in a circuit over contact 575 bottom and back contact of relay 574. Relay 568'm'aintains itself energized over its righthand front contact and sequences'wibch contact 557 bottom and opens on itslei't-hand back contact the circuit for relays 567, 213 and 207.

Ii relay 56a: does; not remain energized over its left-hand winding after its righthand winding is disconnected at sequence switch contact 557 top when sequence switch 550 leaves position 3, relay 563 is energized in a circuit over back contact of relay and sequence switch contact 556 top. Sequence switch 550 is thereby energized in its position 7 over its cimtact 559 top and left-hand front contact of? relay 563, and the line finder is released, as has been described, without interfering with the calling line. If the switches are held up in the exchange, as has been described, and relay 4:77 remains energized, the energization of relay 572 hindered and sequence s itch is held in position 14, whereby relay 56 is energized over sequence switch contact 575, as described, and the calling line is made free, The right-hand winding oi the slow release relay 213 is thereby maintained energized over brush 560, sequence switch contact 558 top and right-hand back contact of relay 567.

What is claimed is 1. In a telephone system, an ethos, an operators position therein, a subscribers line, a selective switch, means for extending the subscribers line to said switch, a trunk, means for controlling the operation of the selective switch to extend said line over said trunk, a connecting circuit, and means controlled from the operators position for rendering the selective switch ineffective when 7 the subscribers line is extended thereto and for extending such line over said connecting circuit. 7

2. In a telephone system, an ofiice, an operators position therein, a subscribers line, a selective switch, automatic switches for extending the subscribefis line to said selective switch, a trunk, a sending mechanism at'the operators position for controlling the operation of the selective switch to extend said line over said trunk, a connect? -ing circuit, and 'r'neans controlled by the operator for renderingthe selectire switch inefiective when the subscribers' line is exline .for controlling the operation of the selective switch to extend the subscribers line over said trunk to the distant ofiice, a connecting circuit outgoing from said first oifice and terminating in the distant ofiice, and means controlled from the operators position in the first oilice for rendering the selective switch ineffective w A the subscribers line is extended thereto a extending such line over said connecting circuit to the operators position in the distant ol'iicle.

4-. a telephone system, an o'llice; crators po ition therein, a subscriber a selective switclnautoniatic meanstending'the suhscribers line to said trunk, means controlling the 0'; of the selective switch to extend s over said trunl', aconnecting circuit, n' auzo iliary device for said selective switch, and means controlled from operators position for operating said auxiliary device, said auxiliary device serving to r nder the-selective switch ineffective when st. riliers line isextended thereto and for extending such. line or 2r said connecting circuit.

A telephone exchange system comprising a plurality of oilices, calling lines terminating at said oilices and adapted to be automatically c ended to operators at such otlices, in, un. the control of said operators tor nrtlier-extending saidcalling lines to called lines, concentration controlling means at said otlices, means responsive to the operation of said concentration controlling means for automatically extending callin "lines terminating in a pluralit of said oliic'es to operators at a single otiice, trunk lines extending between pairs of said an ops line, tor exollice: adapted for norniz'il service therehetwe n, nd means under the control said conce 21621, t'o'modify erators for further extendiip; said calling lines to called lines concentration controlling means at said ollices. means responsive to the operation or" said concentration controlling means for automatically extending calling lines terminating in a plurality of sa d oliices to operators at a single oiilce, trunl: lines extending between pairs of said otlices, group selector switches at the incoming ends of said trunk lines, contacts of group selector switches at the outgoing ends thereof, line findingswitches at said olticcs, means under the'control of s: '.d concentra tion controlling means to modify some of said trunk lines normally serving as outgoing trunk lines from said single oificeto serve as incoming trunk lines in said oiiice for concentration service, and means for disconnecting a trunk line from its group selector switch when modified for concentration service and for extending calling lines finder switches in a concentration ofiice.

T. A telephone exchange system comprising a plurality of O'illCGS, calling lines termin'ating at said oilices and adapted to be automatically extended to operators at such oiiices, means under the control of said operators for further extending said calling lines to called lines, concentration controlling means at said oflices, means responsive to theoperation' of said concentration controlling means for automatically extending calling lines terminating in a plurality of said o'fiices to operators at a single ofiice, trunk lines extending between pairs of said offices, line finder-switches for normally extending a calling line to a connecting circuit and thence to an operator, if idle, and special line finder switches having access to the same alling line and adapted to be put in service when said normally operated normal line finderswitches are out of service, for extending a calling line to a connecting circuit directly connectable to a trunk line, to said single ollice, it said trunk line is idle.

8. In a telephone system, an ofiice, an opcrators position therein, a subscriberg line, a plurality of selective switches, means for extending the subscribe1"s line to said switches, a plurality of trunks, means tor controlling the operation of the selective switches to extend the subscribe-1% line over said trunks. outgoing connecting circuits, one

.tor each of said switches, an auxiliary switch rality of operators positions therein, a subscribers line, a plurality of selective switches, means for extending the suhscribers line to any one of said selective switches, trunk lines, means for controlling the operation of the selective switches to extend the subscribers line over said trunks, a plurality ot outgoing connecting circuits, each individual to certain ones of said selective switches, an auxiliary. switch for each of said selective switches, means at each operators position acting jointly to advance all of said auxiliary switches,and means operated by said auxiliary switches in their advanced condition for rendering the corre sponding selective switches ineiiective when the subscribers line is extended thereto and for extending such line over the corresponding outgoing connecting circuit.

10. In telephone system, an. office, an

operators position therein, a subscribers line, a selective switch, automatic means for extending the subscribers line to said switch, a distant office and an operators position therein, a trunk line interconnecting said ofiices, means for controlling the operation of the selective switch to extend the subscribers line over said trunk to the distant ofiice, a connecting circuit outgoing from the first oii'ice and terminating in the distant office, supervisory means at the first ofiice for notifying the operator therein of the condition of a connection, means controlled from the operators position in the first office for rendering the selective switch ineffective when the subscribers line is extended thereto and for extending such line over said connecting circuit to the operators position in the distant oiiice, and means for rendering said supervisory means ineffective when the subscribers line is extended over said connecting circuit.

11. In a telephone system, an oflice, an operators position therein, a subscribers line, a selective switch, means for extending the subscribers line to said switch, a second oflice and an operators position therein, an

outgoing trunk, means for controlling the operation of the selective switch to extend the subscribers line over said trunk, a connecting circuit extending between said offices normally used for the establishment oteonnections from the second oflice to the first office, an auxiliary switch for said selective swith, means controlled from the operators position in the first oilice for advancing the auxiliary switch provided said connecting circuit is free at the first office, meansoperated by the auxiliary switch for rendering said selective switch ineffective when a subscribers line is extended thereto and for extending Suchline over the connecting circuit to said second oiiice, and means for extending the connecting circuit to the operators position in the second oilice provided the connecting circuit is free at said second oflice.

12. In a telephone system, an oflice, an operators position therein, a subscribers line, selective switches, means for extending the subscribers line to said switches, a second oflice and an operators position therein, trunks outgoing from said first oflice, means for controlling the operation of the selective switches to extend said line over said trunks, a plurality of connecting circuits, one for each of said selective switches extending between said oiiicers, an auxiliary switch for each of said selective switches, means controlled from the operators position in the first ofiice for advancing all of said auxiliary switches provided all the connecting circuits individual to the corresponding selective switches are free at the first oflice, means controlled by any advanced auxiliary switch for rendering ineffective the selective'switch to which it is individual whenthe subscribers line is extended thereto and for extending such line over the corresponding connecting circuit to the second office, and means for extending any of said connecting circuits to the operators position at the second oiilce provided all said connecting circuits are free at the second oiiice.

In witness whereof, I hereunto subscribe my name this 19th day of August A.'D., 1918. i

' LIPA POLINKOWSKY. 

